It is known to use spray nozzles to produce a spray for a wide variety of applications including, for example, coating a surface with a liquid. Typically, in a spray nozzle coating application, liquid is atomized by the spray nozzle into a mist or spray of droplets which is deposited onto a surface or substrate to be coated. The actual droplet size of the atomized liquid and the shape or pattern of the spray discharge from the nozzle can be selected depending upon a variety of factors including the size of the object being coated and the liquid being atomized.
One known technique for atomizing liquids into droplets is to direct pressurized gas such as air into a liquid and thereby mechanically break the liquid down into droplets. In such gas atomization techniques, it can be difficult to control and/or minimize the size and consistency of the droplets. Another known type of spray nozzle is an ultrasonic atomizing nozzle assembly that utilizes ultrasonic energy to atomize a liquid into a cloud of small, fine droplets which is almost smoke-like in consistency. The distribution of droplets within the cloud produced by an ultrasonic atomizer also tend to be advantageously uniform. However, the variety of spray patterns that can be discharged from ultrasonic atomizing nozzles tend to be limited, typically to a conical or cone-shaped pattern. Moreover, because the fine droplets have little mass, they may drift or become dispersed shortly after discharge from the spray nozzle. Because spray patterns made up of such fine droplets are difficult to shape and control, their use in many industrial applications is disadvantageously affected.